#include "types.h"
#include "riscv.h"
#include "defs.h"
#include "date.h"
#include "param.h"
#include "memlayout.h"
#include "spinlock.h"
#include "proc.h"

uint64
sys_exit(void)
{
  int n;
  if(argint(0, &n) < 0)
    return -1;
  exit(n);
  return 0;  // not reached
}

uint64
sys_getpid(void)
{
  return myproc()->pid;
}

uint64
sys_fork(void)
{
  return fork();
}

uint64
sys_wait(void)
{
  uint64 p;
  if(argaddr(0, &p) < 0)
    return -1;
  return wait(p);
}


// 分配内存页空间
// 懒分配：不立即分配内存, 而是只作记录, 在访问到这一部分内存的时候才进行实际的物理内存分配
uint64
sys_sbrk(void)
{
  int addr;
  int n;

  if(argint(0, &n) < 0)
    return -1;

  
  addr = myproc()->sz;

  // 记录n个页面的分配
  if(n >= 0)  myproc()->sz += n;
  // 参数为负，此时要解除分配
  else{
    // 解除分配的参数大于原有的内存
    if(addr + n < 0)  return -1;

    myproc()->sz = uvmdealloc(myproc()->pagetable, addr, addr + n);
  }

  // 不立即分配页面了
  // if(growproc(n) < 0)
  //   return -1;

  // 返回原地址
  return addr;
}

uint64
sys_sleep(void)
{
  int n;
  uint ticks0;

  if(argint(0, &n) < 0)
    return -1;
  acquire(&tickslock);
  ticks0 = ticks;
  while(ticks - ticks0 < n){
    if(myproc()->killed){
      release(&tickslock);
      return -1;
    }
    sleep(&ticks, &tickslock);
  }
  release(&tickslock);
  return 0;
}

uint64
sys_kill(void)
{
  int pid;

  if(argint(0, &pid) < 0)
    return -1;
  return kill(pid);
}

// return how many clock tick interrupts have occurred
// since start.
uint64
sys_uptime(void)
{
  uint xticks;

  acquire(&tickslock);
  xticks = ticks;
  release(&tickslock);
  return xticks;
}
